Neutral stratification

It is known that logarithmic profiles like (1.1) or (3.134) are proved however for only neutral stratification conditions. Some changes in the formulas are required to account for stable or unstable stratification conditions what will be discussed in the Section 3.3.3, formulae (3.141). 

The turbulent mixing model was set up In this case with an Initial temperature profile of neutral stratification between the surface and 80 m, and then allowed to vary according to surface wind stress and heat flux. The Initial deviation of the currents from geostrophy was assumed to be zero. The surface heat flux was allowed to vary dlelly In a sinusoidal manner with a small constant heat flux superimposed, simulating net heating In summer and cooling in winter. 

We have selected two characteristic dispersion conditions for our analyses (1) stable atmospheric stratification (Pasquill-class F) with a wind speed of 2 m/s and (2) neutral atmospheric stratification (Pasquill-class D) with a wind speed of 5 m/s. The mixing layer was estimated to be 200 m for stable and 500 m for neutral stratification. Although the actual meteorological conditions vary continuously during the transport of pollutants, most of the time the actual dispersion conditions varied between the two selected cases. 

The effect of temperature stratification on the atmosphere can be illustrated by considering the different forms a plume may assume. The form of a plume is determined essentially by the relation of the plume release point to any stable, neutral, and unstable layers that may be present the basic forms have been summarized by Slade (1968) and Arya (1999). In a stable layer, vertical mixing of the plume will be limited, and the plume will fan out in the horizontal plane. If a plume is released into a neutral layer capped by a stable layer, the plume will mix vertically throughout the entire depth of the neutral layer. If a plume is released into a neutral layer... 

Heavy rains leach out a portion of the bases in the mull layer and below, most of which are intercepted by the tree roots and returned to the surface again later with the annual leaf fall. Since the leachates are usually nearly neutral in reaction, they extract less mineral matter than where the percolating water is high in organic and nitric acids. This continuous cycling of nutrients accounts for stabilization of the soil with little tendency toward the distinct stratification and impoverishment that is characteristic of true podzols. 

The model applies a Gaussian plume model up to a specified transition distance, which is dependent on atmospheric stability 200 m for unstable, 500 m for neutral, and 1000 m for stable stratification, respectively. Outside this nearby zone, the gradient-transfer approach is used for computing the diffusion in the vertical direction. 

Figure 7.29 Progress of the concentration over time at 100 and 500 m distance from the emission source at 3m/s wind velocity and neutral atmospheric stratification as a consequence of a sudden release of flammable gas.

Chemistry in thepost-MHD shock environment is dominated by the separation between neutral and ionic species, the former being less affected than the latter by the magnetic field. In consequence, the reaction sites are calculated to show abundance stratification depending on the reaction channels. Since the fronts may be broad enough to be spatially resolved, it is possible to study the diffuse-phase ISM shock chemistry observationally in some detail. 

---